No, it’s not possible to play with Xbox ONE FIFA players on the Xbox 360. Cross-play doesn’t work with older systems like the Xbox 360 and PlayStation 3. You can only play with players on the console you are playing on.
Not right now it isn’t, but I can’t promise that it will stay like this though, as Microsoft could announce that it will become backwards compatible in the future. As of right now however, no it isn’t available on Xbox ONE through the Xbox Backwards Compatibly program.
Yes you can, there are multiple different languages on this game to decide from. Once you start the game up you will be prompted almost every time with which language you would like to use to play the game with. The in-game commentators however, I do not know whether there is many languages available for them or not.